Conventionally, toners having particle sizes of 10 μm or so have been used. With the advancement of higher image qualities in electrophotography in the recent years, toners have been desired to have smaller particle sizes. However, since the toners having smaller particle sizes have strong aggregating force between the toners as compared with those having conventional particle sizes, the toners would not be favorably dispersed during the treatment of external addition, whereby the adhesive strength of the external additive is likely to be lowered. When the external additive having such a weak adhesive strength is freed during a use of a toner in a machine, the durability of the toner may be worsened in some cases.
On the other hand, as a process for preparing a toner, a means of mixing a roughly pulverized kneaded product with a fluidity improver such as a silica or an inorganic oxide, and pulverizing the mixture is proposed (see JP2002-131979 A and JP2004-126260 A).